Niall lived 600-odd years ago. The common ancestor off all R1b1c7 men lived
more like 4000 years ago. I consider it extremely unlikely that Niall is my
ancestor, and though I acknowledge that if he was in fact R1b1c7 he is a
cousin of some degree, I do not consider that such evidence as we have
constitutes proof that Niall was R1b1c7. Maybe he was, maybe not. There are
sure a bunch of modern-day O'Neills that are not R1b1c7. Who is to say they
are not the "true" descendants of Niall and the R1b1c7s among us are
descended from folks who were living in Ireland and Scotland long before the
Gaels (including Niall's ancestors) showed up?

Historians aren't even sure Nial existed as an historic personage; but there
is one thing that stands out in Irish history - all of the major Ui Neill
chieftains said to descend from Nial appear to be R1b1c7 with the curious
exception of the O'Neills. That also includes the so-called Connachta, alleged to
be kinfolk of the Ui Neill in Irish pedigrees. The O'Neills in the Trinity
database actually fall into three groups: R1b1c7 (8); the main O'Neill group
(13); plus a third non-R1b1c7 group different from the main group (6).
There are also a couple of I haplogroup O'Neills and one R1a. It therefore
appears there were three different O'Neill of Ulster clusters with a few
non-matching haplogrous thrown in the mix.

The rumors about an O'Neill bastard named Kelly revolved around Conn
O'Neill, earl of Ulster, 1542. George HIll relates the tale in his "Plantation of
Ulster."

"Conn O'Neill, who accepted an English earldom in the year 1542, and died in
1559. This Ulster prince fell prey to certain English servitors, including
the Bagenalls, who were able to intermeddle with his family affairs, and who
eventually induced him to adopt the son of a Dundalk blacksmith, named Kelly,
to the exclusion of his only legitimate son, Shane O'Neill.

One of our best irish archaeological authorities - O'Donovan - believed that
Con O'Neill's heir was really the son of a blacksmith, and this his [the
heir's] son, who is known in history as Hugh O'Neill, second earl of Tyrone, was
not, therefore, an O'Neill at all."

But as I recall, the Trinity study estimated the common ancestor of the main
group of O'Neills to have lived about 900 A.D., or close to the time of
Domhnall 'of Armagh' Ua Neill, the Irish High King and ancestor of the O'Neills
who died in 980 AD. If this TMRCA is anywhere near correct it would appear to
be too early to connect with a 16th century NPE.

As I've mentioned before, we have a distinctive DNA pattern in our
MacLochlainn of Donegal dataset. The same pattern occurs in some Dohertys,
Gallaghers and O'Boyles. We've recently found some Neels/Neals who also have the
same pattern. It's also an unusual DNA pattern amongst the R1b1c7 and seems
centered in Donegal/Tyrone/Derry, the heartbed of Ui Neill territory in NW
Ireland.

But to return to the question of the O'Neills - Seamus O Ceallaigh in
"Gleanings from Ulster History" analyzed their pedigree and referred to their
"murky" past, a quote picked up by some modern historians. You can read O
Ceallaigh's article here:

There is a possibility at least that any NPE that may have occurred in the
O'Neill line happened long ago, perhaps as early as the 12th century, when
the earliest traceable ancestor of the O'Neills, Aedh 'the lazy youth" Ua
Neill suddenly appeared on the scene and somewhat miraculously wrested control of
the Cenel Eoghain and the northern Ui Neill from the then dominant
MacLochlainn kings of Aileach.

The final word has yet to be said about the O'Neills. No one really knows
what happened. The DNA of the main group of non-matching O'Neills doesn't
seem to match much of anything in Ireland. In later times the O'Neills split
into three main branches, Tyrone, Clannaboy and the Fews in Armagh. A NPE
could conceivably have occurred in any of these branches at almost any time.
Or we could have a case of surname adoption as seen so often in the great
Scottish clans. In addition to the Kelly bastard tales, there are stories by
English writers of the 17th century which describe peasant Irish women naming
their sons O'Neill in the hopes of securing a future for their sons. And other
stories about men claiming themselves to be O'Neills (every strong man in
Ulster proclaimed himself to be an O'Neill).

Part of the problem we have with the O'Neills is none of the current
O'Neill chieftains have yet been tested although there are plenty of poseurs out
there.